This invention relates to a limited slip differential which is actuated to limit the relative rotational speed between two driven shafts above a predetermined amount.
Limited slip differentials are known for providing rotational drive to two output shafts. In particular, such differentials are often used to drive the axles of motor vehicles. A limited slip differential allows relative rotation between two output shafts under certain circumstances. For example, when a vehicle turns, the output shaft of the outer wheel typically turns at a higher rotational speed than the output shaft of the inner wheel. A limited slip differential allows this relative rotation. If one of the wheels begins to slip, however, the relative rotational speed between the output shafts of the two wheels exceeds a predetermined limit. A limited slip differential resists such relative rotational speed.
One known limited slip differential employs a viscous coupling which "monitors" any relative rotation between the two output shafts. Should the relative rotational speed exceed a certain limit, viscous fluid in the viscous coupling expands to create an axial force against an actuation member. In turn, the actuation member is forced against, and engages a friction clutch, directly connecting the first and second output shafts.
There are drawbacks to such prior art differentials. Relying on fluid expansion does not provide fine control over the amount of relative rotation required before clutch actuation. Further, the reliance on the expanding fluid also may not be easily controlled to allow variation of the desired limit on relative rotational speed.